If you see downy mildew on impatiens, please contact researcher

impatiens with white coating of downy mildew
Impatiens with downy mildew. Photo courtsy Margery Daughtrey
early signs of downy mildew on impatiens
Impatiens showing early signs of downy mildew. Photo courtesy Margery Daughtrey

by Connie Oswald Stofko

Downy mildew on impatiens has been found in Lockport, and if you find it on your impatiens plants, too, a Cornell researcher wants your help.

Margery Daughtrey, senior extension associate with the Section of Plant Pathology and Plant-Microbe Biology at Cornell University, has been providing us with information on this disease that will kill impatiens since my first article on impatiens in 2012.

Daughtrey works in the the Long Island Horticultural Research & Extension Center, directed by Mark Bridgen. They are doing research to try to find plants that are able to resist downy mildew and need help from gardeners.

They need live samples of impatiens with downy mildew.

“Keep your eyes peeled and let me know if you see it, please!” Daughtrey wrote.

Watch your plants for symptoms of the disease. You might see early signs, such as yellowing leaves, like the single plant in the second photo. If you see the white coating on the backs of the leaves, like in the first photo, that’s downy mildew.

If you think your impatiens has downy mildew, put a bucket over the plant (so the disease doesn’t spread), but don’t pull the plant out. Email Daughtrey at mld9@cornell.edu and she will tell you what she needs.

There’s also a related plant, Impatiens balsamina, also sometimes referred to simply as balsam, that can also get the disease, and Daughtrey would like samples from that as well.

Balsam is sort of an old fashioned plant that might not be as popular as it once was. Instead of mounding like Impatiens walleriana, it grows upright in a spike and has pointed leaves. Impatiens balsamina is susceptible to the disease, but it isn’t killed outright like regular impatiens is.

On balsam, instead of a coating on the back of the leaves, you’ll see small spots on the leaves. Again, if you find the disease, contact Daughtrey at mld9@cornell.edu.

Daughtrey said the disease has been found this year in Long Island and Saratoga Springs as well as in Lockport.

Symptoms of very stunted growth followed by white sporulation on the undersurfaces of leaves have shown up on plants grown in flowerbeds where the disease was known to occur in earlier years—additional evidence that oospores in the soil will keep this disease around, she said.

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3 Comments on “If you see downy mildew on impatiens, please contact researcher

  1. My impatiens have been stricken with downy mildew. They had been planted in four seperate containers and did well all summer, until now. This happened very suddenly. I am in Nassau County.

  2. My impatiens have been stricken with downy mildew. They had been planted in four seperate containers and did well all summer, until now. This happened very suddenly. I am in Nassau County.

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